First time water softener buyer looking for advice!

I'm looking to get a water softener for a relative and I'd greatly appreciate some advice. I've been doing a lot of research, so I think I have a pretty good idea of what I need, but I'd really appreciate advice from the experts. Here's their details:

- 2 bathroom house
- no jacuzzi or anything like that, only a dishwasher and a washing machine
- max flow rate ~12gpm
- 1" plumbing
- according to their water bill, water usage ranged from 11k to 19k gallons per month - average is about 16k. They don't do any outdoor watering, car washing, etc., so this is all internal home use. Don't know if this matters, but thought I should mention it. Their household is actually only 3 adults. However, their daughter's family (2 adults, 2 kids) spends the weekends there - which I suppose is why their usage is so high.

Now for their water data. This data comes from a Quality Report done by the city. There are 6 water sources that combine, and the data is provided as ranges, so I took the weighted averages of all the sources.

According to my calculations, they need to remove between 60k and 100k grains per week - average is about 84k. I think this would indicate that they need either 3.5 or 4 cu.ft. of resin. However, I've talked to 3 local companies and everyone has said that's way to big for residential. They say those sizes are primarily for commercial, and they all have recommended either 2.0 or 2.5 max, so now I'm kinda second-guessing myself and wondering if I'm missing something. On the other hand, there's a considerable jump in price between 2.5 and 3.5, so if 2.5 will suffice I would go with that. Would there be any downside to 2.5, aside from it regenerating more often?

I was using 7 days in my calculations - forgot to add a day for reserves. Yeah - I was surprised at their usage too (this is my relatives household, not mine), but that's what their water bill says. it actually lists usage in "hundred cubic ft" units, and states that 1 unit equals 748.05 gallons, so I calculated their usage in gallons by multiplying the two.

My household usage isn't as high as theirs, but is quite a bit higher than normal (I live 2 blocks from my relative). Is it possible our utility bills are't accurate? should I trust the utility bill, or use the "accepted" average of 75 gallons/person?

Twin tank 9100SXT would be my recommendation, probably a 1.5 cu. ft. per tank. Plenty of flow, no reserve calculations needed, and it only uses 2.4 GPM during backwash, so the flow loss to the house would not be noticed when the system regenerates.

They need to do a water usage study to determine if something else is going on there. Slab leak, toilets, etc.

Twin tank 9100SXT would be my recommendation, probably a 1.5 cu. ft. per tank. Plenty of flow, no reserve calculations needed, and it only uses 2.4 GPM during backwash, so the flow loss to the house would not be noticed when the system regenerates.

They need to do a water usage study to determine if something else is going on there. Slab leak, toilets, etc.

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Dittohead - is there a reason you would recommend twin tanks over a single 3.0 cu.ft. unit? From a price perspective, twin tanks seem to bump the price up by several hundred dollars.

It is based on salt and water efficiency. Your application is unusual in that it has some considerable variances in water usage that may cause a system to need to regenerate with a lot of the reserve capacity unused (wasted). We try to design single tank residential systems with 6 days or more between regenerations. This minimizes the lost capacity. A twin alternating system does not have a reserve since it regenerates any time of the day. The 9100SXT is an exceptional valve that will last for many years with minimal service.

Just a quick calculation, not highly accurate but the general idea is there.

600 GPD x 25 grains hardness x 365 days = approximately 5,500,000 grains annually. Estimating a 20% loss due to unused reserve = approximately 1,000,000 grains innefficiency. 1,000,000 / 24,000 = 42 cu. ft. of resin not used, regenerated w/ 8# per cu. ft. = approximately 350# additional salt usage per year. This may not justify the additional cost of a twin tank system, but it is the right way to do it. Assuming your numbers are correct, I have run these numbers very conservatively. The savings will probably be much higher.

Jkats, on the other hand he is not telling you that a twin tank softener uses capacity/salt/water to regenerate because they all use softened water for each regeneration of each tank forever.

And I've been in and around this business since 1987 and ditto is the only person I've ever heard make the claim he is making about not using the reserve of a two tank type softener. Even Kinetico salesmen don't go on like that but...

He is suggesting a twin with 1.5 cuft tanks. The highest hardness is 28 gpg not the 25 he used. And he used 600 gals per day. So have him tell you how many times a day a 1.5 cuft tank will be regenerated. How many lbs of salt will be used. And make him tell you how many lbs are used just to regenerate each tank with softened water. Then compare that to his supposed annual reserve not used salt use of 350 lbs.

IOWs you want to know the total salt used for both type softeners and you might as well ask how many additional gallons of water the twin tank will use over the larger two tank type.

Your relatives may have a toilet tank flapper valve leak or a fill valve allowing overflow of the stand pipe 24/7. There usually is a water height line on the stand pipe about an inch below the top meaning the water should be about an inch below the top of the tube.

Reserve capacities of single tank systems are a formula that professionals use to estimate when a softener needs to regenerate so as to maintain soft water. Older electromechanical metered units required a simple math equation (estimate) based on an assumed gallons used per day. If a softener can treat 1000 gallons between regenerations, and the application uses 600 gallons per day, the system would need to regenerate daily, leaving potentially 400 gallons of capacity that is simply lost (waste). A twin system does not need a reserve since it will regenerate until the softener metering system gets to 0 gallons, then it will simply switch to the standby tank. The depleted tank will regenerate and standby until it is needed. Twin systems usually use soft water regeneration, but since a regeneration cycle on a modern softener can easily be set to as little as approx. 50 gallons per regeneration. From a technical standpoint, that water is mostly not even calculated since the gain in efficiency of the second tank for the last 2/3's of the brine cycle and the rinse cycle are not taking away the same amount of gallons as regenerating with hard water would do. Twin alternating units are primarily used in commercial applications, but in high hardness, or high water use residential applications they make perfect sense.

Another way to maintain a higher efficiency is to use a variable brining system. These have their flaws, but on paper they work very well. They have become a popular alternative to twin tank systems in smaller commercial applications, but it would take a couple thousand words to explain the pros and cons. Watts has done an excellent job with their variable brining system and is one that I have seen in the feild in some really bad applications and it has been able to maintain soft water and a much higher efficiency than a non variable brining design. still, a twin alternating system would be the correct system for you.

You are using a bogus example with a softener that allows 1000 gals between regenerations when the daily water use is 600 gallons. How about trying again with a correctly sized two tank softener for Jkats.

And you didn't get into how much salt is used each regeneration of a twin tank softener because softened water is used for each regeneration of each tank. And you didn't mention how many regenerations the 1.5 cuft each tank twin would use compared to the correctly sized two tank.

Hey guys - thanks so much for all the great info - I didn't realize this could be so complex! I guess my first order of business will be to check out if they have any obvious leaks, since this will affect the usage rate and consequently the softener size. Assuming the data is correct though, Dittohead - you are recommending twin 1.5 cuft tanks; Gary - I checked out the link in your sig, and according to the chart on that page, I assume you would recommend a 4.0 cuft single tank system?

Hey guys - thanks so much for all the great info - I didn't realize this could be so complex! I guess my first order of business will be to check out if they have any obvious leaks, since this will affect the usage rate and consequently the softener size. Assuming the data is correct though, Dittohead - you are recommending twin 1.5 cuft tanks; Gary - I checked out the link in your sig, and according to the chart on that page, I assume you would recommend a 4.0 cuft single tank system?

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Correct, a 4 cu. ft. softener would be a 16" diameter x 65" tall tank. That would be a little overkill for a residential application. The recommended low flow for that large of a tank is 4.2 GPM, that would require 3 faucets to be turned on at the same time for the system to meet its minimum recommended low flow.

Variable reserve and variable brining are completely different and are not related in any way. Variable reserve simply allows a softener to make a mathematical estimate of when it should regenerate to be as efficient as possible while still wasting a certain portion of the systems capacity.

Last note, a twin alternating design can regenerate multiple times per day if needed with no negative affect. We sell many hot water 9000 twin alternators for large undersink dish washer applications where space is extremely limited so the system are considerably undersized and they regenerate multiple times per day. This is not ideal, but it is also not a problem.

Variable brining is a softener adjusting the amount of salt the system regenerates with in order to only regenerate the amount of resin that has been used. Similar to topping off a gas tank, instead of just putting 20 gallons in whether the tank is empty or not, and anything past full just goes on the ground.

Variable brining has its problems and we don't recommend it if you can get a softener past 5 days between regenerations. Some of our customers have been using variable brining very successfully for many years in place of twin alternating designs in commercial applications.

I just had to get my two cents in on this one. I see that the twin alternating is a good fit for your home and your friends down the street. I would look at the water meter to ensure your water usage is at what the utility says it is. Check for leaks via the water meter also is a good idea (there should be a flow indicator like a small triangle spinning slowly if you have a leak). Finally there is a product out there that is a twin alt tank system but uses a new tech called TWEDO that saves a lot of water in the regeneration process. The company is called Clearion Water Systems, you should be able to google it since advertising on forums is a no, no. The fleck head is good but they haven't embraced any new advancement for that valve in a number of years now.

The 9100SXT actually has many advances recently, but for the most part, they do so little to increase efficiency compared to how efficient the system already is. Twin alternating sensor technology is about as efficient as you can get, but is the tiny gains in efficiency worth the cost in complexity and additional purchase price? Ultra efficient systems are nothing new, the problem is the math. Once you get to a certain efficiency level, it is simply a matter of tiny little advances. The real savings in the future is going to come from using less water in the house.